Human Skull And Two-Legged Walk Evolved Together

The evolution of the human skull went hand in hand with walking on two legs as per a new study. According to researchers from the University of Texas at Austin and Stony Brook University, the discovery has the potential to solve one of the most intriguing mysteries of human evolution -- the development of bipedalism or walking on two legs.

The connection between the evolution of human skull and two-legged walk has been deemed as controversial by researchers. Primordial humans climbed trees and also walked on the ground, which offered them the flexibility of movement and also the ability to evade predators. Scientists believe that humans made the gradual transition from climbing trees to walking upright between 6 million and 3 million years ago. The development of bipedalism in humans also coincided with significant physical changes such as evolution of longer legs. About 1.9 million years ago, Homo erectus had thigh and leg bones that had evolved for walking on two legs to cover long distances -- quite similar to modern humans.

Humans are different from other primates due to their foramen magnum -- the large hole at the base of the skull that the spinal cord passes through -- which is shifted forward. According to researchers, this difference is the result of bipedalism evolution, where the skull had to be balanced directly on top of the spine to help in walking.

Now, according to a study published in the Journal of Human Evolution, researchers Chris Kirk and Gabrielle Russo have provided convincing evidence that the forward shifted foramen magnum is not a feature exclusive to modern humans or their primordial ancestors but bipedal mammals in general.

“This question of how bipedalism influences skull anatomy keeps coming up partly because it is difficult to examine the various hypotheses if you only focus on primates,” Kirk said in a press release. “However, when you look at the full range of diversity across mammals, the evidence is compelling that bipedalism and a forward-shifted foramen magnum go hand-in-hand.”

A link between bipedalism and the foramen magnum’s position is hugely significant because the connection could help researchers know more about extinct hominids and whether they walked on two feet like modern humans or four feet like modern apes. Subsequently, the understanding can also help provide a map of bipedalism evolution in the future.